It's not that simple.
For example;
If the bill was clearly unconstitutional (and yes I do believe the Legislature would pass such a bill), then no.
If it was clearly ridiculous, and I can't think of an example right now (and you screaming its anti 2a doesn't count), then no.
But this leaves a huge grey area and the exact wording of the bill, along with whether or not the Legislature has the votes to override, will come into play.
And this brings up the simple fact that vetoing any bill that the Legislature certainly has the votes to override would be a pointless use of political capital.
Politics is a complicated game.
In NH the former Governor didn't sign the CC bill thinking the Legislature couldn't force it through and the people wouldn't hold it against her too much. She expended political capital (the support of the people) and didn't sign. But she was only half right and is now gone. In MA the majority of the voters want, or are willing to accept greater gun control. So his letter was the best Baker could do without pissing off the voters he needs to stay in office. Not to mention that had he made it an issue it is far more likely any Legislative action would not have been a positive thing.